PATTERNS OF VARIATION IN BODY‐MASS OF THE BLACK‐EYED BULBUL <i>PYCNONOTUS BARBATUS</i>

Crowe, Timothy M.; Rebelo, Anthony G.; Lawson, Walter J.; Manson, A. J.

doi:10.1111/j.1474-919x.1981.tb04036.x

Cited by 7 publications

(4 citation statements)

References 13 publications

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“…These results, although from body mass records that were uncorrected for size in four bulbul subspecies with different geographic ranges, were interpreted as being consistent with Bergmann’s rule and the productivity hypothesis (Niles 1973 ). Our results do not negate these conclusions (Crowe et al 1981 ), but we argue they may have been arrived at by chance because the occurrence of heavier birds (rather than birds with larger body surface area to volume ratio) in cooler environments does not necessarily imply conformity to Bergmann’s rule. Our raw body mass data also showed a negative non-significant trend with temperature (Fig.…”

Section: Discussioncontrasting

confidence: 81%

“…Hence, the correlation between body surface area to body mass ratio and aridity in the Common Bulbul is unlikely to be due to differences in net primary productivity, as frequently suggested for other animals (Yom-Tov and Geffen 2006 , 2011 ). Geographical variation in body mass has previously been reported for the Common Bulbul (Crowe et al 1981 ; Brittion 1972 ; Hanmer 1978 ): bulbuls tend to be heavier in localities with lower environmental temperatures and high productivity. These results, although from body mass records that were uncorrected for size in four bulbul subspecies with different geographic ranges, were interpreted as being consistent with Bergmann’s rule and the productivity hypothesis (Niles 1973 ).…”

Section: Discussionmentioning

confidence: 82%

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Temperature and aridity determine body size conformity to Bergmann’s rule independent of latitudinal differences in a tropical environment

et al. 2018

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Bergmann’s rule, defined as the tendency for endotherms to be larger in colder environments, is a biophysical generalization of body size variation that is frequently tested along latitudinal gradients, even though latitude is only a proxy for temperature variation. We test whether variation in temperature and aridity determine avian body size conformity to Bergmann’s rule independent of latitude differences, using the ubiquitous Common Bulbul Pycnonotus barbatus, along a West African environmental gradient. We trapped 538 birds in 22 locations between latitudes 6 and 13°N in Nigeria, and estimated average body surface area to mass ratio per location. We then modelled body surface to mass ratio using general linear models, with latitude, altitude and one of 19 bioclimatic variables extracted from http://www.worldclim.org/bioclim as predictors. We sequentially dropped latitude and altitude from each model to obtain the R2 of the resultant models. Finally, we compared the R2 of univariate models, where bioclimatic variables predicted body surface area to mass ratio significantly (14 out of 19), to multivariate models including latitude, altitude and a bioclimatic variable, using the Wilcoxon matched pairs test. We found that multivariate models did not perform better than univariate models with only bioclimatic variables. Six temperature and eight precipitation variables significantly predicted variation in body surface area to mass ratio between locations; in fact, 50% (seven out of 14) of these better explained variation in body surface area to mass ratio than the multivariate models. Birds showed a larger body surface area relative to body mass ratio in hotter environments independent of latitude or altitude, which conforms to Bergmann’s rule. Yet, a combination of morphometric analyses and controlled temperature-exposure experiments is required to prove the proposed relationship between relative body surface area and thermoregulation in endotherms.Electronic supplementary materialThe online version of this article (10.1007/s10336-018-1574-8) contains supplementary material, which is available to authorized users.

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Section: Discussioncontrasting

confidence: 81%

Section: Discussionmentioning

confidence: 82%

Temperature and aridity determine body size conformity to Bergmann’s rule independent of latitudinal differences in a tropical environment

et al. 2018

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“…We can not directly compare bill length, as it was measured differently from our study. These data are in agreement with Bergmann's rule, which proposes that within-species body size is positively correlated with latitude and colder climate (Bergmann 1847) and which has been confirmed in other passerines from southern Africa, such as the Cape Sparrow Passer melanurus (Slotow and Goodfriend 1996) and the Dark-capped Bulbul Pycnonotus tricolor (Crowe et al 1981 15.0 ± 0.3 14.8 ± 0.5 14.7 ± 0.5 14.3 ± 0.5 14.6 ± 0.4 4.31** Fat score 3.1 ± 1.0 3.1 ± 0.9 3.3 ± 1.3 3.5 ± 1.3 3.4 ± 1.0 0.37 Muscle score 1.9 ± 0.3 1.9 ± 0.4 1.9 ± 0.3 1.9 ± 0.4 1.9 ± 0.3 0.08 * P < 0.05, ** P < 0.01, *** P < 0.001 …”

Section: Resultssupporting

confidence: 90%

Morphometrics of White-browed Sparrow-Weavers Plocepasser mahali in south-western Zimbabwe

Leitner

Mundy

Voigt

2009

Ostrich

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This paper describes size and body condition of individuals in a population of the cooperatively breeding White-browed Sparrow-Weaver Plocepasser mahali in south-western Zimbabwe in relation to the birds' social status within their colony. We undertook measurements and observations of colour-ringed individuals during two successive breeding seasons. Each colony was organised into a dominance hierarchy, with a single dominant breeding pair and male and female subordinates. Our results showed that males were generally larger than females in body mass, wing and bill length. Within each sex size was not significantly related to dominance status. Body condition did not vary by sex, age or status.

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“…For example, across its geographical range, 59 different populations of a common African species (Common Bulbul Pycnonotus barbatus ) have been shown to display a degree of plasticity in their weight variation in response to varied environmental conditions. Individual birds tended to be heavier at sites with lower temperatures and populations responded to increased seasonality by increasing their body mass in colder months (Crowe et al. 1981).…”

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confidence: 99%

Patterns of seasonal and yearly mass variation in West African tropical savannah birds

Cox

Brandt

Mcgregor

et al. 2011

Ibis

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Birds in the northern hemisphere usually increase mass reserves in response to seasonal low temperatures and shorter day length that increase foraging unpredictability and so starvation risk. In the lowland tropics, relatively low temperatures and short day lengths are absent and so the risk of starvation may be reduced, leading to much smaller seasonal effects on mass. Nevertheless, other factors such as high temperatures and water and food availability may vary greatly between tropical wet and dry seasons, leading to variable starvation risk and seasonal mass effects. Using data collected from 47 species of birds caught over a 10-year period in a tropical savannah region in West Africa we tested for seasonal variation in mass in response to a predictable, strongly seasonal tropical climate. Many species (91%) showed seasonal variation in mass, and this was often in a clear annual pattern that was constant across the years. Many species (89%) varied their mass in response to seasonally predictable rainfall. Annual variation in mass was also important (45% of species). Relatively few species (13%) had a seasonal pattern of mass variation that varied between years. Feeding guild or migratory status was not found to affect seasonal or annual mass variation. Seasonal mass change was on average 8.1% across the 21 species with a very large sample size and was comparable with both northern and southern temperate species. Our study showed that biologically significant consistent seasonal mass variation is common in tropical savannah bird species, and this is most likely in response to changing resource availability brought about by seasonal rainfall and the interrupted foraging response due to the constraints of breeding.

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PATTERNS OF VARIATION IN BODY‐MASS OF THE BLACK‐EYED BULBUL PYCNONOTUS BARBATUS

Cited by 7 publications

References 13 publications

Temperature and aridity determine body size conformity to Bergmann’s rule independent of latitudinal differences in a tropical environment

Temperature and aridity determine body size conformity to Bergmann’s rule independent of latitudinal differences in a tropical environment

Morphometrics of White-browed Sparrow-Weavers Plocepasser mahali in south-western Zimbabwe

Patterns of seasonal and yearly mass variation in West African tropical savannah birds

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